Properties of Air

Background• Weather is affected by the unique

properties of air. These properties include:

• Air has mass and volume• Air expands to fill a space• Air expands and rises when heated• Air contracts and sinks when cooled

• Air exerts pressure• Air moves from areas of high pressure

to areas of low pressure

Activity One• Properties of Air• Do you think air affects the weather? • How?• You are going to conduct several

investigations to further understand the properties of air that affect weather conditions and climate.

Activity Two• Take a deep breath and observe others

as you do so.• When you take deep breaths, what do

you notice about your chest?• Why does your chest expand, or get

bigger, when you take a breath?

• Everyone breathes air, and when we take deep breaths, air enters our lungs and expands our chests.

• Now blow up a balloon and notice what happens to the balloon.

• Compare with the balloons that are not blown up.

• Why did the balloon get bigger?• What is inside the balloon?• Even though air cannot be seen, it still

takes up space.• When the air is inside the balloon, what

shape does it have?

• What shape does the air take on when it is in your chest?

• Several empty containers…..• Is there anything inside these

containers?• What shape does the air take on in

these containers?

• Air takes on the shape of the container that it is in.

• What does the term volume mean?• The amount of space taken up by an

object.• Does air have volume?

• Is the amount of air in a small container the same as in a large container?

• Air has volume.• Let the air out of your balloon and feel it

whooshing by.

• Divide into partners.• Blow up balloon and hold it tightly, have

partner squeeze the balloon to feel the pressure of the air inside it.

• Now let the air out a feel the air as it escapes, and notice the decrease in pressure as the air escapes.

• AIR EXERTS PRESSURE!!!

Activity ThreeAir Exerts Force

Each student get a balloon and blow it up and hold it secure.• What will happen if you let go of your

balloon?• Predict and test.

• Why did the balloon move?• What is a FORCE?• Does the air in the balloon exert force?• Repeat experiment and point balloon in

a different direction.

• The air inside the balloon makes the balloon move because air exerts force.

• The balloon will always move in the direction opposite to the hole where the air is escaping.

Air has Mass• Blow up two balloons and tie and place

on either side of a balance scale.• Are the balloons heavy?• Do you think that air has mass?• What do you think will happen if you

pop one of the balloons?

• Pop one with a pin and see what happens.

• Why do you think the end of the scale with the inflated balloon attached to it moved downward?

• Which end of the scale has more mass?• What does this prove about air?

Air Expands When Heated and Contracts

When Cooled• Balloons again and tie.• Is the air from your lungs warm or cool?• What do you think will happen to the air

in your balloon if you put the balloon in a cold place?

• Measure the circumference of your balloon and record.

• Now place the balloon in a cold space.• What happened to the balloons?• Why do you think the balloons got

smaller?• What do you think the circumference of

your is now?

• Measure and record.• What do you think will happen if you put

your balloon in a warm place?• Test!• Measure again.

Expansion and Contraction of Air

• The air has particles that move farther apart when heated, causing the air to take up more space.

• Air becomes less dense as the molecule or particles move farther apart.

• When air is cooled, the molecules or particles move closer together, causing the air to take up less space.

• Air becomes more dense as the molecules or particles move closer together.

Warm Air Rises, Cold Air Sinks

• Cut a piece of paper in a circle to make a snake.

• Tie with a thread.• What do you think will happen if I place

the spiral over a heat source such as a light bulb?

• Test

• Why do you think the spiral is beginning to spin?

• What is happening to the air around the light bulb?

• What happens to air as it is heated?

• Expansion and contraction of air.• As air is heated it expands.• The molecules move farther apart.• At the same time, the air becomes less

dense and, therefore, lighter.• This warm air rises.

• In this activity with the spiral, the air is heated by the light bulb.

• This causes the warm air to rise.• As the warm air currents rise, they

cause the spiral to turn.

• If warm air rises, what do you think happens to cold air?

• Cold air sinks because it is more dense.• Map Activity sheet 4.5.1